AbstractWe have investigated the heteroepitaxy of indium nitride (InN) directly grown on nitridated sapphire substrates having different orientations. Growths were performed on C, A, M and R‐plane oriented sapphire in order to analyse the substrate orientation effect on the structural, optical and electronic properties of as‐grown InN. Atomic force microscopy imaging on the InN epilayers revealed different surface morphologies with crystallites well organized along a crystalline orientation of the layer. We have studied the structural anisotropy observed in these layers analysing high‐resolution X‐ray diffraction rocking curve experiments as a function of the in‐plane beam orientation. A‐plane oriented InN grown on R‐plane sapphire substrate shows a polarized photoluminescence anisotropy, with an anisotropy percentage of about 33%.